Re: [PATCH] crypto: lib/sha256 - Disable SIMD

[Eric Biggers]

On Fri, May 16, 2025 at 07:48:52PM +0800, Herbert Xu wrote:
> On Fri, May 16, 2025 at 07:34:06PM +0800, Herbert Xu wrote:
> > 
> > So what's happened is that previously if you call sha256_update
> > from lib/crypto it would only use the generic C code to perform
> > the operation.
> > 
> > This has now been changed to automatically use SIMD instructions
> > which obviously blew up in your case.
> 
> In the interim you can go back to the old ways and disable SIMD
> for lib/crypto sha256 with this patch:
> 
> ---8<---
> Disable SIMD usage in lib/crypto sha256 as it is causing crashes.
> 
> Reported-by: Borislav Petkov <bp@xxxxxxxxx>
> Fixes: 950e5c84118c ("crypto: sha256 - support arch-optimized lib and expose through shash")
> Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

That's silly.  We should just fix x86's irq_fpu_usable() to return false before
the CPU is properly initialized.  It already checks a per-cpu bool, so it
shouldn't be too hard to fit that in.

Using the generic SHA-256 code explicitly is also an option, but ideally the
regular functions would just work.

- Eric